Ned Arnel Mencía was born the seventeenth of eighteen children in San Pedro Sula, Honduras. At the time of his birth, his Mexican mother, Magdelena Mencía, was engaged in a domestic dispute with his Honduran father, Roberto Holness, and declined to give her son his biological father's last name.[1] The name appearing on his birth certificate is "Ned Arnel Mencía", although Mencia has said that out of respect for his biological father he went by the Holness name anyway, and was known as Ned Holness until he was 18 years old.[citation needed]

Mencia was raised in East Los Angeles, California by his aunt Consuelo and uncle Pablo Mencia. By his own admission, staying out of trouble was difficult while growing up, but with the help of his family he excelled in school and stayed out of gangs. He majored in electrical engineering at California State University, Los Angeles, but left early to pursue a career in comedy after a successful performance at an open mic night at The Laugh Factory. He also has an older brother named Joseph Mencia who often appears on Mind of Mencia.

Mencia currently lives with his wife, Amy, in the Los Angeles area in California. They have one child, Lucas Pablo Mencia.[citation needed]

Mencia was a quick success at such venerated LA stand-up venues as The Comedy Store and The L.A. Cabaret. This led to appearances on The Arsenio Hall Show and Buscando Estrellas, where he attained the title "International Comedy Grand Champion." Then, in 1994, Mencia was chosen to host HBO's latino comedy showcase Loco Slam.

Mencia followed up Loco Slam by hosting Funny is Funny! on Galavision in 1998. He would continue to do stand-up, including a very successful tour in 2001 with Freddy Soto and Pablo Francisco, "The Three Amigos." Mencia also did two half-hour specials on HBO, the second of which won him a CableACE Award for Best Stand-Up Comedy Special. After the release of his first comedy album by Warner Records, Take A Joke America, Mencia performed his break-out performance on Comedy Central Presents in 2002.

By the time his career began to take off in the early 2000s, Mencia was also working as an actor doing guest appearances in the television shows Moesha and The Shield, and starring in the film Outta Time and the animated show The Proud Family.

At the end of 2004, Comedy Central began talks with Carlos Mencia for his own program shortly after their renewal of comedian Dave Chappelle's contract for Chappelle's Show in March of 2005, prior to Chappelle’s April 28, 2005 departure from the production of Chappelle’s Show and subsequent trip to Africa. In March 2005, Comedy Central announced Mencia's own half-hour comedy show, Mind of Mencia. The show mixed Mencia's stand up comedy with sketch comedy, much like the highly popular Chappelle's Show. The show achieved moderate success in its first season and was brought back for a second season in the spring of 2006, becoming Comedy Central’s second highest rated program behind South Park, and again for a third season that summer.

Maxim recently named Mencia as the 12th-worst comedian of all time, although television viewers themselves had voted him into 2nd place of the Top 25 stand-up comics in Comedy Central's 2006 "Stand Up Showdown".

Mencia is a frequent guest on the Opie and Anthony radio show on XM Satellite Radio and CBS Radio. He took part in in first Opie and Anthony's Traveling Virus Comedy Tour in 2006.

Mencia starred in a Super Bowl XLI commercial for Bud Light, which was the #1 most replayed commercial according to TiVo. Mind of Mencia is produced by Nedlos, a portmanteau of Mencia's birth name and stage name.

Comedian Joe Rogan wrote a post on his website publicly accusing Mencia of being a plagiarist, alleging that Mencia stole jokes from a number of comedians.Notably on February 10, 2007 Rogan confronted Mencia on stage at the Comedy Store on Sunset and continued his allegations of plagiarism. Rogan posted a video of the altercation with audio and video clips from other comedians including George Lopez and Ari Shaffir among others.Rogan has also posted audio and video clips of Mencia's interviews and joke routines being compared on his blog. George Lopez has accused Mencia of plagiarizing his material. In an interview on The Howard Stern Show, Lopez accused Mencia of plagiarizing 13 minutes of his material in Mencia's HBO special. He also claimed he had a physical altercation with Mencia over the alleged plagiarism,. The only joke that Lopez has publicly specified was stolen and used on Mencia's HBO special was a Taco Bell joke. Comedian Ted Sarnowski countered this claim, stating that the joke he performed on radio in 1988 was later taken and used without permission by Lopez, the radio station's resident comic. Sarnowski claims to have given Mencia permission to use the joke, yet Lopez later began referring to Mencia as a "thief" over the joke Lopez allegedly plagiarized.